1. Field of the Invention
Apparatuses consistent with the present invention relate to an autostereoscopic display and, more particularly, to an autostereoscopic display that can display a stereoscopic image without lowering resolution and can reduce crosstalk between left and right images.
2. Description of the Related Art
In general, a stereoscopic image is made based on the principle of stereo image sensing by two eyes. Binocular parallax which occurs due to the eyes being separated by about 65 mm from each other is one of the factors for producing a stereoscopic image. Three-dimensional (3D) displays are divided into displays using glasses and glassesless displays. Glassesless stereoscopic displays produce a 3D image by separating an image for a left eye from an image for a right eye without the use of glasses. In general, glassesless stereoscopic displays are divided into parallax barrier displays and lenticular displays.
Parallax barrier displays and lenticular displays are similar to each other in that a specific optical plate, for example, a barrier or a lenticular lens, is located in front of or behind a display panel to spatially separate images having different viewpoints. The images from the different viewpoints are separated and form certain viewing zones, and thus a user can see a stereoscopic image only when the two eyes of the user are located in the corresponding viewing zones.
Parallax barrier displays alternately print images, which are to be seen respectively by left and right eyes, in a vertical pattern in order to see the printed images using an extremely thin vertical lattice column, i.e., a barrier. By doing so, a vertical pattern image to be seen by the left eye and a vertical pattern to be seen by the right eye are distributed by the barrier and the left and right eyes see images at different viewpoints so as to perceive a stereoscopic image.
FIG. 1A illustrates a related art parallax barrier autostereoscopic display. Referring to FIG. 1A, a barrier 10 having vertical-lattice-shaped slits 5 and masks 7 is disposed in front of a liquid crystal panel 3 having left-eye image information Ln and right-eye image information Rn that respectively correspond to a viewer's left eye LE and right eye RE. An image is separated through the slits 5 of the barrier 10. The left-eye image information Ln to be input to the left eye LE and the right-eye image information Rn to be input to the right eye RE are alternately arranged in the horizontal direction of a screen on the liquid crystal panel 3.
Pixel columns having the left-eye image information Ln and pixel columns having the right-eye image information Rn form one set, and pixel columns on left and right sides of the slits 5 become pixels at different viewpoints to produce a stereoscopic image. For example, referring to FIG. 1B, left-eye image pixels L1, L3, L5, L7, and L9 of odd columns in the left-eye image information Ln and right-eye image pixels R1, R3, R5, R7, and R9 of odd columns in the right-eye image information Rn form one set and are input to the liquid crystal panel 3. Here, right-eye images composed of the odd columns and left-eye images composed of the odd columns constitute a first field image.
According to such a method, since images are formed through the slits 5 and blocked by the masks 7, the right-eye images of the odd columns and the left-eye images of the odd columns are provided to the right eye and the left eye, respectively.
Since only the images of the odd columns are displayed, the resolution of the display on the whole as well as 3D image brightness deteriorates. There is a sequential barrier method that can increase resolution.
Barriers used for separating viewing zones are generally fabricated by printing periodically repeated stripes on a transparent film or a glass substrate. However, barriers can also be fabricated in an electrical way using a liquid crystal barrier. In this case, the positions of slits and masks are electrically shifted by actively switching the shape of the liquid crystal barrier.
FIG. 2A illustrates a related art autostereoscopic display with slits 5 and masks 7 whose positions are shifted from their counterparts of FIG. 1A by switching a liquid crystal barrier 10. Referring to FIG. 2B, left-eye image pixels L2, L4, L6, L8, and L10 of even columns and right-eye image pixels R2, R4, R6, R8, and RIO of even columns are input to the liquid crystal panel 3. In this case, right-eye images composed of the even columns and left-eye images composed of the even columns are provided to the right eye and the left eye, respectively. Here, the right-eye images of the even columns and the left-eye images of the even columns constitute a second field image.
The resolution of a stereoscopic image can be improved by sequentially displaying the first field image of the odd columns and the second field image of the even columns.
The liquid crystal panel 3 comprises m×n pixels arranged in a matrix, m data lines and n gate lines, which electrically intersect each other, and thin film transistors (TFTs) formed at intersections of the data lines and the gate lines. An image signal is scanned in the vertical direction of the liquid crystal panel 3. FIG. 3 illustrates an image signal scanned over time. At a first time T1, a first field image signal and a second field image signal are simultaneously transmitted to the liquid crystal panel 3. At a second time T2, a first field image signal is transmitted to the liquid crystal panel 3. At a third time T3, a second field image signal and a first field image signal are simultaneously transmitted to the liquid crystal panel 3. At a fourth time T4, a second field image signal is transmitted to the liquid crystal panel 3.
During a first-half period (first period Tf) of one frame period T, a first field image is displayed, and as an image signal is scanned, a first field image and a second field image exist together for some time. During a second-half period (second period Tb) of the frame period T, a second field image is displayed, and a first field image and a second field image exist together for some time. FIG. 4 is a perspective view illustrating the liquid crystal barrier 10. Referring to FIG. 4, the related art liquid crystal barrier 10 includes odd column cells 10a and even column cells 10b that are alternately arranged in the horizontal direction of the liquid crystal barrier 10. The liquid crystal barrier 10 further includes a first electrode 20 for controlling the transmittance of the odd column cells 10a, a second electrode 22 for controlling the transmittance of the even column cells 10b, and a common electrode 24 commonly connected to the odd column cells 10a and the even column cells 10b, with all of the electrodes 20, 22 and 24 being connected to a barrier controller 25, so as to control the transmittances of the respective column cells. Accordingly, even when a first field image signal and a second field image signal exist together as an image signal is scanned on the liquid crystal panel 3, any one of a first barrier state for a first field image and a second barrier state for a second field image is enabled.
FIGS. 5A and 5B are perspective views for explaining the operations of a liquid crystal panel 3 and a liquid crystal barrier 10′. Referring to FIG. 5A, while the liquid crystal panel 3 includes a panel region 3a for a first field image and a panel region 3b for a second field image, the barrier 10′ is driven for only a second field image. Referring to FIG. 5B, an image of the panel region 3b for the second field image is separated by the barrier 10′ for the second field image into a left-eye image and a right-eye image to form a stereoscopic image, but an image of the panel region 3a for the first field image passes through the barrier 10′ for the second field image such that left-eye images are provided to a user's right eye and right-eye images are provided to his or her left eye, thereby causing crosstalk between the right-eye images and the left-eye images and resulting in a decrease in display brightness and image quality.